Growth hormone secretion in stalk-sectioned rats

1991 ◽  
Vol 124 (6) ◽  
pp. 700-706 ◽  
Author(s):  
Jun Kamegai ◽  
Ichiji Wakabayashi ◽  
Hitoshi Sugihara ◽  
Shiro Minami ◽  
Taiko Kitamura ◽  
...  
Keyword(s):  
Adrenal Glands ◽  
Gh Deficiency ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Male Rats ◽  
Gh Secretion ◽  
The Face ◽  
Prolactin Response ◽  
Plasma Gh ◽  
Trough Levels

Abstract. Idiopathic pituitary GH deficiency appears to result from neonatal disruption of hypophyseal portal vessels in the majority of patients. To examine the mechanism of GH deficiency associated with the disease, the effect of pituitary stalk section on GH secretion was studied in rats. Adult male rats were subjected to stalk section without inserting an impermeable membrane between the cut ends. They were studied 3 to 4 weeks after surgery. In stalk-sectioned rats, pituitary weight, body weight and hypothalamic SRIH content were significantly reduced as compared with sham-operated rats. Hypothalamic GHRH content, plasma T3, T4, corticosterone and testosterone levels, and weights of testes remove and adrenal glands were comparable in the two groups. Plasma GH profiles of sham-operated rats showed characteristic periodic pulses occurring at 2.5-3 h intervals with intervening trough period. In stalk-sectioned rats, plasma GH levels were low with small fluctuations, but GH levels were significantly higher than trough levels of sham-operated rats. The amount of GH secreted during a 6-h period as measured by planimetry was significantly reduced. To ascertain the regeneration of hypophyseal portal vessels, post SRIH rebound in GH secretion, which requires the presence of endogenous GHRH, was examined. Withdrawal of exogenous SRIH infusion triggered a large rebound GH secretion whose magnitude did not differ between groups. In stalk-sectioned rats, GH response to met-enkephalin analogue, FK 33-824, was not observed, whereas prolactin response to the secretagogue was observed in the majority of rats. It appears that in stalksectioned rats, hypophyseal portal circulation is re-established, but GHRH release from the hypothalamus is impaired in the face of sufficient supply of other hypophysiotropic hormones.

Oral dexamethasone administration: new pharmacological test for the assessment of growth hormone secretion

1994 ◽  
Vol 131 (6) ◽  
pp. 598-601 ◽  
Author(s):  
Jaime Pineda ◽  
Pedro Martul ◽  
Felipe F Casanueva ◽  
Carlos Dieguez ◽  
Itxaso Rica ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Gh Deficiency ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Prepubertal Children ◽  
Gh Secretion ◽  
Oral Dexamethasone ◽  
Pharmacological Test ◽  
Plasma Gh ◽  
Normal Adults

Pineda J, Martul P, Casanueva FF, Dieguez C, Rica I, Loridan L. Oral dexamethasone administration: new pharmacological test for the assessment of growth hormone secretion. Eur J Endocrinol 1994;131:598–601. ISSN 0804–4643 Acute intravenous (iv) dexamethasone administration has been described recently as a new test for the diagnosis of growth hormone (GH) deficiency. In the present study, a new protocol of dexamethasone administration was evaluated. Twelve normal adults and 18 normal prepubertal children were studied. The dexamethasone iv test was performed in six adults at a dose of 4 mg and 12 children at a dose of 2 mg/m2. Blood samples were collected 15 min before, at time zero and every 15 or 30 min during 5 h, resulting in a total of 16 samples. In the remaining six adults and six children, 8 and 4 mg, respectively, of dexamethasone were administered orally at the subject's home, and blood sampling started 90 min later when they arrived at the hospital. Plasma GH was measured by radioimmunassay. The dexamethasone-induced GH response (mean ± sem, μg/1) to the iv or oral protocol did not differ in either the adults (iv 8.2 ± 2.1; oral 8.0 ± 1.6) or the children (iv 14.9 ± 1.3; oral 13.6 ± 1.8). It is concluded that the simpler protocol of acute oral dexamethasone administration hereby presented can be a safe and suitable test of GH secretion. J Pineda, Sección de Endocrinologia Pediátrica, Hospital de Cruces, 48903 Baracaldo (Vizcaya), Spain

scholarly journals Obestatin Partially Affects Ghrelin Stimulation of Food Intake and Growth Hormone Secretion in Rodents

Endocrinology ◽  
2007 ◽  
Vol 148 (4) ◽  
pp. 1648-1653 ◽  
Author(s):  
Philippe Zizzari ◽  
Romaine Longchamps ◽  
Jacques Epelbaum ◽  
Marie Thérèse Bluet-Pajot
Keyword(s):  
Food Intake ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Male Rats ◽  
Pituitary Cells ◽  
Gh Secretion ◽  
Freely Moving ◽  
Stimulation Of

Administration of ghrelin, an endogenous ligand for the GH secretagogue receptor 1a (GHSR 1a), induces potent stimulating effects on GH secretion and food intake. However, more than 7 yr after its discovery, the role of endogenous ghrelin remains elusive. Recently, a second peptide, obestatin, also generated from proteolytic cleavage of preproghrelin has been identified. This peptide inhibits food intake and gastrointestinal motility but does not modify in vitro GH release from pituitary cells. In this study, we have reinvestigated obestatin functions by measuring plasma ghrelin and obestatin levels in a period of spontaneous feeding in ad libitum-fed and 24-h fasted mice. Whereas fasting resulted in elevated ghrelin levels, obestatin levels were significantly reduced. Exogenous obestatin per se did not modify food intake in fasted and fed mice. However, it inhibited ghrelin orexigenic effect that were evident in fed mice only. The effects of obestatin on GH secretion were monitored in superfused pituitary explants and in freely moving rats. Obestatin was only effective in vivo to inhibit ghrelin stimulation of GH levels. Finally, the relationship between octanoylated ghrelin, obestatin, and GH secretions was evaluated by iterative blood sampling every 20 min during 6 h in freely moving adult male rats. The half-life of exogenous obestatin (10 μg iv) in plasma was about 22 min. Plasma obestatin levels exhibited an ultradian pulsatility with a frequency slightly lower than octanoylated ghrelin and GH. Ghrelin and obestatin levels were not strictly correlated. In conclusion, these results show that obestatin, like ghrelin, is secreted in a pulsatile manner and that in some conditions; obestatin can modulate exogenous ghrelin action. It remains to be determined whether obestatin modulates endogenous ghrelin actions.

Effect of actively immunizing sheep against growth hormone-releasing hormone or somatostatin on spontaneous pulsatile and neostigmine-induced growth hormone secretion

1995 ◽  
Vol 144 (1) ◽  
pp. 83-90 ◽  
Author(s):  
E Magnan ◽  
L Mazzocchi ◽  
M Cataldi ◽  
V Guillaume ◽  
A Dutour ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Body Weight ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Physiological Role ◽  
Gh Secretion ◽  
Igf I ◽  
Plasma Gh ◽  
Hypophysial Portal

Abstract The physiological role of endogenous circulating GHreleasing hormone (GHRH) and somatostatin (SRIH) on spontaneous pulsatile and neostigmine-induced secretion of GH was investigated in adult rams actively immunized against each neuropeptide. All animals developed antibodies at concentrations sufficient for immunoneutralization of GHRH and SRIH levels in hypophysial portal blood. In the anti GHRH group, plasma GH levels were very low; the amplitude of GH pulses was strikingly reduced, although their number was unchanged. No stimulation of GH release was observed after neostigmine administration. The reduction of GH secretion was associated with a decreased body weight and a significant reduction in plasma IGF-I concentration. In the antiSRIH group, no changes in basal and pulsatile GH secretion or the GH response to neostigmine were observed as compared to controls. Body weight was not significantly altered and plasma IGF-I levels were reduced in these animals. These results suggest that in sheep, circulating SRIH (in the systemic and hypophysial portal vasculature) does not play a significant role in pulsatile and neostigmine-induced secretion of GH. The mechanisms of its influence on body weight and production of IGF-I remain to be determined. Journal of Endocrinology (1995) 144, 83–90

Prolonged fasting or clonidine can restore the defective growth hormone secretion in old dogs

1989 ◽  
Vol 121 (2) ◽  
pp. 177-184 ◽  
Author(s):  
Silvano G. Cella ◽  
Valerio Moiraghi ◽  
Francesco Minuto ◽  
Antonina Barreca ◽  
Daniela Cocchi ◽  
...  
Keyword(s):  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Peak Frequency ◽  
Prolonged Fasting ◽  
Total Peak Area ◽  
Gh Secretion ◽  
Age Related ◽  
Adrenoceptor Agonist ◽  
Baseline Conditions ◽  
Plasma Gh

Abstract. Age-related changes in GH secretion were studied in the dog. In preliminary experiments, administration of GH-relasing hormone (GHRH-40, 2 μg/kg, iv) or the α2-adrenoceptor agonist clonidine (4 μg/kg, iv) elicited significantly higher plasma GH rises in 3 to 4 years old than in 10 to 14 years old beagle dogs. The pulsatile patterns of GH secretion in both young and old dogs under baseline conditions and after prolonged fasting or clonidine administration were studied. Samples were taken every 10 min from 09.00 to 15.00 h from five young and five old dogs of both sexes. Under baseline conditions, GH peak frequency, total peak area, and integrated GH secretion were significantly lower in old than in young dogs. In old dogs, 5-day complete fasting or 14-day clonidine administration (75 μg/dog, po, twice daily) increased the frequency and amplitude of spontaneous GH bursts, the total peak area, and the integrated GH secretion. After either stimulus, the GH secretory pattern was quantitatively and qualitatively indistinguishable from that of young dogs under baseline conditions. Similarly, the foregoing indices were significantly increased in young dogs by either stimulus, except for the inability of clonidine to affect peak frequency. These data demonstrate that the defective GH secretion in old dogs is not irreversible, since it is normalized when old dogs are exposed to central nervous system-directed stimuli.

Exercise Provocation Test for Growth Hormone Secretion: Methodologic Considerations

2008 ◽  
Vol 20 (4) ◽  
pp. 370-378 ◽  
Author(s):  
Alon Eliakim ◽  
Dan Nemet
Keyword(s):  
Growth Hormone ◽  
Gh Deficiency ◽  
Current Knowledge ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Provocation Test ◽  
Pharmacological Agents ◽  
Laboratory Exercise ◽  
Gh Secretion ◽  
Artificial Nature

The diagnosis of Growth Hormone (GH) deficiency in children with short stature is complex, and in certain cases, might be very difficult. Most of the provocative tests used to evaluate GH deficiency use pharmacological agents. The artificial nature of the pharmacological tests and the possibility that these tests might not always reflect GH secretion under normal physiological conditions provides the impetus for a more physiologic test. Exercise is one of the important GH releasing physiological stimuli. This review will summarize the current knowledge on the methods for performing laboratory exercise provocation test for GH secretion in children. In addition to recommendations of more standardized exercise protocols and environmental considerations, we will also focus on GH responses to exercise in unique populations such as obese children.

Somatostatin tonically inhibits growth hormone secretion in domestic fowl

1986 ◽  
Vol 111 (1) ◽  
pp. 91-97 ◽  
Author(s):  
S. Harvey ◽  
S.-K. Lam ◽  
T. R. Hall
Keyword(s):  
Growth Hormone ◽  
Domestic Fowl ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Passive Immunization ◽  
Inhibitory Effect ◽  
Gh Secretion ◽  
Basal Plasma ◽  
Plasma Gh

ABSTRACT Passive immunization of immature chickens with sheep somatostatin (SRIF) antiserum promptly increased the basal plasma GH concentration and augmented TRH-induced GH secretion. Although exogenous SRIF had no inhibitory effect on the basal GH concentration in untreated birds or birds pretreated with non-immune sheep serum, it suppressed the stimulatory effect of SRIF immunoneutralization on GH secretion. These results suggest that SRIF is physiologically involved in the control of GH secretion in birds, in which it appears to inhibit GH release tonically. J. Endocr. (1986) 111, 91–97

Physiological control of growth hormone secretion by thyrotrophin-releasing hormone in the domestic fowl

1985 ◽  
Vol 105 (3) ◽  
pp. 351-355 ◽  
Author(s):  
H. Klandorf ◽  
S. Harvey ◽  
H. M. Fraser
Keyword(s):  
Domestic Fowl ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Physiological Control ◽  
Thyrotrophin Releasing Hormone ◽  
Releasing Hormone ◽  
Gh Secretion ◽  
Normal Sheep Serum ◽  
Plasma Gh

ABSTRACT Immature cockerels (4- to 5-weeks old) were passively immunized, with antiserum raised in sheep, against thyrotrophin-releasing hormone (TRH). The administration of TRH antiserum (anti-TRH) at doses of 0·5, 1·0 or 2·0 ml/kg lowered, within 1 h, the basal concentration of plasma GH for at least 24 h. The administration of normal sheep serum had no significant effect on the GH concentration in control birds. Although the GH response to TRH (1·0 or 10·0 μg/kg) was not impaired in birds treated 1 h previously with anti-TRH, prior incubation (at 39 °C for 1 h) of TRH (20 μg/ml) with an equal volume of anti-TRH completely suppressed the stimulatory effect of TRH (10 pg/kg) on GH secretion in vivo. These results suggest that TRH is physiologically involved in the hypothalamic control of GH secretion in the domestic fowl. J. Endocr. (1985) 105, 351–355

Growth hormone secretion in the horse: unusual pattern at birth and pulsatile secretion through to maturity

1993 ◽  
Vol 138 (1) ◽  
pp. 81-89 ◽  
Author(s):  
F. Stewart ◽  
J. A. Goode ◽  
W. R. Allen
Keyword(s):  
Cavernous Sinus ◽  
Post Partum ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Peripheral Circulation ◽  
Pulse Frequency ◽  
Synthetic Analogue ◽  
Pulsatile Secretion ◽  
Gh Secretion ◽  
Plasma Gh

ABSTRACT A heterologous radioimmunoassay was developed and validated for the measurement of horse GH in plasma. It utilized recombinant-derived bovine GH as the radiolabelled ligand, a guinea-pig anti-porcine GH serum as first antibody and pituitary-derived horse GH as standard. Cross-reactivites were high with all of the pituitary and recombinant-derived GH preparations tested (49–140%) and very low (<0·3%) with horse FSH, LH and prolactin. A synthetic analogue of GH-releasing factor(1–29) stimulated the expected pattern of GH release in foals. Plasma GH concentrations in foals were low at birth (<20 ng/ml) but rose sharply to a definite and, in most cases, very large peak (18–195 ng/ml) during the first 30–40 min post partum, followed by a steady decline to basal levels again by 60–100 min post partum. GH secretion was clearly pulsatile in all older foals tested (2 weeks, 1 month and 4 months of age) and in six adults (three mares and three stallions), all bled at 15-min intervals for 7–8 h. Basal levels and pulse amplitudes were higher in foals than in adults and pulse frequency was higher in stallions than in mares (3–5 pulses/8 h vs 1–2 pulses/8 h). Pulsatile secretion was further characterized in one mare by simultaneous sampling of jugular vein and pituitary cavernous sinus blood. Peak GH concentrations in cavernous sinus blood draining the pituitary gland were more than tenfold higher than the corresponding peak concentrations in peripheral circulation. The patterns of GH release in the horse therefore appear to be similar to those reported in other species with the exception of the low values at birth followed by the dramatic rise and fall in concentrations during the first hour post partum. Journal of Endocrinology (1993) 138, 81–89

Diminution of pulsatile growth hormone secretion in the domestic fowl (Gallus domesticus): evidence of sexual dimorphism

1988 ◽  
Vol 119 (1) ◽  
pp. 101-109 ◽  
Author(s):  
R. J. Johnson
Keyword(s):  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Pulse Height ◽  
High Amplitude ◽  
Sexually Dimorphic ◽  
Male And Female ◽  
Gh Secretion ◽  
Baseline Values ◽  
Plasma Gh ◽  
Meat Type

ABSTRACT Temporal plasma GH secretory patterns were measured in cannulated male and female meat-type chickens of two commercial strains at 17, 38 and 60 days of age. Pulse height, amplitude and baseline values were similar in both male and female chickens at 17 days of age, with high amplitude and low baseline values. However, by 38 days of age pulsatile GH secretion was not detectable in females, whereas males exhibited a continued pulsatile secretory pattern similar to that at 17 days of age. Pulsatile GH secretion was not evident in either males or females at 60 days of age. These results clearly demonstrate a sexually dimorphic ontogeny of GH secretion in meat-type chickens. J. Endocr. (1988) 119, 101–109

Stimulation of in-vivo growth hormone secretion in young chickens by rat hypothalamic growth hormone-releasing factor and synthetic analogues

1986 ◽  
Vol 108 (3) ◽  
pp. 413-416 ◽  
Author(s):  
C. G. Scanes ◽  
S. Harvey ◽  
J. Rivier ◽  
W. Vale
Keyword(s):  
Growth Hormone ◽  
Domestic Fowl ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Gh Secretion ◽  
Structure Activity ◽  
In Vivo Growth ◽  
Plasma Gh ◽  
Stimulation Of

ABSTRACT Rat hypothalamic GH-releasing factor (rhGRF), at doses between 0·1 and 10 μg/kg, increased plasma GH concentrations in immature domestic fowl 5–10 min after i.v. injection. Sodium pentobarbitone anaesthesia blunted the GH responses to rhGRF, although in both conscious and anaesthetized chicks the maximal responses were induced by a dose of 1 μg rhGRF/kg. The stimulatory effect of rhGRF on in-vivo GH secretion was less than that provoked by corresponding doses of human pancreatic GRF, but greater than that elicited by two rhGRF analogues, (Nle27)-rhGRF(1–32) and (Nle27)-rhGRF(1–29). These results demonstrate that the chicken pituitary is responsive to mammalian GRF and provide evidence of structure-activity relationships of GRF in the domestic fowl. J. Endocr. (1986) 108, 413–416

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